This invention relates to cleaning methods and apparatus, and more particularly relates to methods and means for cleaning interior surfaces of storage tanks and the like, and also stripping rubber linings and the like affixed to these interior surfaces.
It is well known in the prior art that a diversity of commodities are transported by land in railroad tank cars, truck trailers, transport tankers, etc. It is also well known in the prior art that there are special purpose railroad tank cars and the like which are lined with rubber and the like, to prevent contamination, chemical reactions, etc. Similarly, after arriving at the intended destination, these commodities must be stored in lined storage tanks and the like.
Prior to being filled or loaded with a particular commodity, a tank car, storage tank and the like must be thoroughly cleaned for health and safety reasons. Tanks or cars with linings must, of course, also be cleaned and, indeed, such linings may be stripped and replaced prior to being filled or loaded with another commodity. Such cleaning and stripping have heretofore conventionally been both labor-intensive and time-consuming.
During typical manual cleaning, the flow of liquid through hand-held hoses is limited to volumes of less than approximately 7 gallons per minute. This throughput is not only limited by a worker's handling ability, but also is limited by the unstable standing conditions in a slippery, conventional rounded-bottom tank car. Indeed, considering that typical manual car-wash volumes of water are only 2 gallons per minute at low pressures of 1,500 psi, a 7 gallon per minute flow presents a considerable challenge to a worker, particularly within the confines of a tank car and the like. Furthermore, there are hazards to workmen from splashing chemicals, debris, fumes, and even explosions. Thus, in addition to being an inherently hazardous and slow method of cleaning tank cars, such manual methods are inherently nonuniform and unreliable.
Accordingly, there have been several attempts in the art to automate the cleaning and stripping of tank cars and the like. To clean the interior of a tank car with reduced human intervention, however, requires that a suitable apparatus either be a permanent member thereof or be inserted and then assembled therein. As should be evident to those conversant with the art, entry into a railroad tank car is routinely available through a narrow manway located on top thereof or could be rendered expedient through a specially designed wall or side panel or door. But, of course, a tank car with such a specially designed panel or door would necessitate structural modifications and would be susceptible to contamination and leakage.
An apparatus designed to eliminate or minimize such danger to workmen is illustrated by Hulbert in U.S. Pat. No. 3,571,985. Specifically intended to clean tank car linings with an abrasive material like sand, Hulbert discloses an apparatus consisting of a support structure affixed to the ends of a tank car using hydraulics and pneumatics. A pneumatic pump provides for longitudinal movement of a carriage along the support structure, while another pneumatic pump simultaneously provides for independent rotational movement of a plurality of nozzles. Drive means are also provided for the manual control of linear carriage advancement and rotational nozzle spray pattern. A vacuum pump removes debris from the floor of the tank car. Since considerable time appears to be prerequisite to assembling the Hulbert apparatus, it is probably intended not to be portable, but to be a relatively permanent fixture in a tank car.
As another example, Saxonmeyer, in U.S. Pat. No. 3,461,889, teaches an apparatus for washing railway tank car interiors which provides for the entry through a side door in the tank car of a platform movably mounted by a base and a carriage movably mounted with respect to the platform. A boom assembly mounted on the carriage controls the spray of liquid about a vertical axis through a plurality of nozzles. The Saxonmeyer apparatus includes sensing arms to provide semi-automatic operation by limiting its washing operation only to times when a side edge of the tank car door opening is not contacted.
While improving the prior railway tank car cleaning art, the Hulbert and Saxonmeyer devices have provided only limited arcuate manipulation of the spray nozzles and require structural modifications to a railroad tank car. Guignon et at., in U.S. Pat. No. 3,444,869, disclose a jet cleaning device which attempts to improve the effectiveness and nature of the spray for cleaning purposes. Based upon a complicated plurality of oscillatable nozzles, this device has a corresponding plurality of streams of cleaning liquid which is directed to the internal surfaces of a tank car. The sizes of these streams depends upon the distances of the plurality of nozzles from the internal surfaces therefrom.
Another improvement in the nozzle manipulation art is disclosed by Jaeger in U.S. Pat. No. 3,895,756. In particular, there is disclosed a method and apparatus for cleaning vessels which not only enables presetting control means to accommodate a vessel's dimensions, but also enables programming a sequence of nozzle movements. The Jaeger apparatus is lowered into a tank car through its manway and the assembly connected by liquid pressure lines to a control device and to a source of pressurized cleaning fluid. A high pressure spray nozzle is mounted for universal movement relative to two perpendicular axes. Separate hydraulic actuators are connected to and activated from a remote control device, which is air operated and with means for adjusting the speed and degree of sweep of the spray nozzle, thereby enabling a spray of any configuration to be generated. Thus, in addition to providing more versatile manipulation and control of spray nozzles, the Jaeger apparatus is portable and is inserted into a tank car through its manway.
Similarly, in U.S. Pat. No. 3,001,534, Grant teaches a portable apparatus for cleaning a tank car by being inserted thereinto. A baseplate temporarily replaces a tank car's dome cover and supports an assembly extending into the interior of the car and carrying rotating spray heads. These spray heads are driven by an electric motor and rotate about two orthogonal axes, thereby permitting water spray throughout a tank car's interior. Thus, in addition to improving the prior art with a portable top-insertable apparatus, the Grant apparatus is easily positioned within the tank car and directs a controllable, compound water spray pattern throughout the interior thereof using swivel means. The number of revolutions of the swivel means is determined by the relative ratios of two sets of pinions and gears.
Further improvements in the prior art are disclosed by Looper and Maton. In U.S. Pat. No. 4,244,523, Looper teaches a top-inserting apparatus for conveniently and inexpensively cleaning rubber-lined tank cars. This apparatus consists of a fixed frame for supporting a tiltable frame from which extends a pivotally mounted wash nozzle assembly containing a cleaning liquid tube at the end of which is connected spray nozzles. The spray jets operate simultaneously on longitudinal and transverse axes of the tank car promoting thorough cleaning thereof. Similarly, in U.S. Pat. No. 4,341,232, Maton discloses a tank cleaning apparatus which limits the rotation of top-insertable spray arms to 180.degree. instead of the conventional 360.degree.. By only rotating spray arms through 180.degree. during the washing cycle, matter dislodged from the interior of a tank car is prevented from being forced upon already cleaned surfaces because a spray pattern is formed which directs such dislodged material to one end of the car or to its bottom.
There have been similar attempts to improve the cleaning and stripping art related to storage tanks and the like. For example, Krajicek et al teach a remote-controlled tank cleaning robot in U.S. Pat. No. 4,817,653. Assembled on-site, this robot is hydraulically powered to reach all interior tank surfaces using an interdependent series of elbow joint structures. But a worker is required to be present within the tank during cleaning operation. In U.S. Pat. No. 4,716,917, Schmidt discloses an apparatus for cleaning tanks on a ship, using nozzles which are rotatably affixed to nozzle holders which are located at various elevations on a vertical standpipe. A rotary and vertically reciprocating drive rotates the nozzles, thereby cleaning the interior tank surfaces.
Similarly, Hatley teaches in U.S. Pat. No. 3,874,594 an apparatus which cleans tankers using a housing which rotates about a vertical axis. Obliquely attached to this housing is a nozzle which rotates about a horizontal axis, for spraying both proximate and distant interior tank wall, using gears and clutch mechanisms. Patenaude teaches in U.S. Pat. No. 4,595,419 an apparatus for purging radioactive contamination from internal surfaces of a steam generator constructed of typical U-tube configuration, using programmed robotic arm movements and an ultrasonic transducer. The ultrasonic transducer is remotely controlled to optimize scrubbing action of the robotic arms.
In U.S. Pat. No. 5,087,294, Rechtzigel teaches an apparatus for cleaning storage tanks constructed with a floating roof, which includes an elongated nozzle having a pair of spray jets radially opposing each other. Vertical legs are attached to the floating roof and engage the bottom of the tank. This elongated nozzle rotates about a vertical axis and emulsifies the accumulated material residing on the bottom of the tank. The circular pattern of rotation is controlled by a series of radially spaced openings in the floating roof.
As another contribution to the tank cleaning art, Sloan discloses an apparatus and method limited to cleaning sludge from the bottom of a liquid storage tank in U.S. Pat. No. 5,037,486. This self-propelled sludge-cleaning apparatus is assembled on-site and hydraulically propelled along the bottom of a tank using a tether line which is connected to a control assembly. Similarly, Moran, in U.S. Pat. No. 4,828,625, teaches a floating-roof structure located above the sludge with tubular sleeves with remote legs for support. These sleeves are located immediately above the sludge for recirculating pressurized fluid through the sludge.
Fumess et al, in U.S. Pat. No. 4,407,678, disclose an apparatus having a vertically positioned casing with diametrically opposed nozzles, for removing sludge from storage tanks. This pair of nozzles is configured to produce a liquid spray in only one plane as the housing rotates horizontally. The housing is situated just above the tank floor. In U.S. Pat. No. 5,248,095, Rankin et at. disclose a rotating nozzle intended to be used for water blasting. This nozzle rotates relative to a horizontally-positioned longitudinal shaft and discharges high pressure water in a circular path with a continuously changing point of impact. Being inclined relative to the water stream, the Rankin nozzle continuously changes direction of movement. In U.S. Pat. No. 4,770,711, Deal et at. disclose a method for cleaning chemical sludge from storage tanks, using a frame which moves along the bottom of the tank on a pair of endless chain belts and directs a fluidizing agent at the sludge to form a pool and then to discharge the sludge.
Notwithstanding these improvements in the tank cleaning and stripping art, there is still not available an automatic or semi-automatic and reliable apparatus and method for cleaning storage tanks and the like and for stripping the linings therein contained. It would be advantageous for an apparatus to be sufficiently portable to be completely inserted through an existing manway and then be conveniently and quickly assembled therein. It would also be advantageous for such an apparatus to be readily configured and maneuvered so as to reach all of the interior surfaces of storage tanks of various diameters.
Those skilled in the art would also appreciate the utility of an apparatus capable of generating and accurately controlling a high pressure and high volume liquid spray such that the entire interior surfaces of a storage tank and the like would be effectively treated, even containing a lining thereon. Such effective liquid spray would preclude the present conventional use of abrasive cleaning of linings, thereby significantly prolonging the longevity thereof. It would be further advantageous if such apparatus were driven within the storage tank by a non-electrical motor to avoid a potential safety hazard due to sparks causing combustion or explosion.
Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, and improved means and techniques are provided which are useful for cleaning and stripping residue, contaminants, debris, etc. from all of the interior surfaces in a storage tank and the like, such that the means may be conveniently inserted into a storage tank through its manway and, after quick assembly thereof, hydraulically erectified to reach all of the interior surfaces of the tank, and then be preset for automatic or semi-automatic cleaning and/or stripping operation.